The invention relates to an antenna array having a plurality of primary radiator modules arranged vertically one above the other.
Antenna arrays having primary radiators arranged vertically one above the other are known per se. In the case of dual-polarized antennas, these primary radiators arranged one above the other can emit or receive two orthogonal polarizations. Furthermore, these primary radiators, which are arranged to form an array, can also be referred to as primary radiator modules. Such modules may comprise, for example, simple dipoles, slots, planar radiator elements or so-called patch radiators, as are known, for example, from EP 0 685 900 A1 or from the prior publication xe2x80x9cAntennen [Antennas], 2nd Part, Bibliographisches Institut, Manheim [sic]/Vienna/Zurich, 1970, pages 47 to 50. The dipole arrangements are preferably dipoles arranged in a cruciform (cross) shape (cross-dipoles) or double dipole arrangements whose plan view is a square structure (dipole square).
Dual-polarized antennas are, furthermore, also known, for example from WO 98/01923.
In the cited prior art, primary radiator modules having the same radiation characteristics are in each case combined to form arrays. In contrast to this, the interconnection of antennas having different radiation characteristics is used to supply different regions. In this case, there is a disadvantage that the phase relationship in the overlapping area of the two polar diagrams is undefined, leading alternately to cancellation or additive superimposition. The polar diagram that results from this in the overlapping region is in this case unknown.
Multiband antennas are also known, in which different primary radiators for different frequency bands are interconnected with the aim of broadening the frequency band of the antenna. However, in this case, each radiator acts at a different frequency.
The interconnection of different frequency radiators with a continuously varying size extent is also known for the purpose of broadening the frequency band (for example, logarithmic antennas or leakage wave antennas).
Particularly in the mobile radio area, there is a requirement to design and to set antennas such that their polar diagram corresponds to a desired, predetermined half-value width. The setting of the horizontal half-value width of linear, vertically stacked arrays, which correspond to the typical configuration of such base station antennas for mobile radio, is in this case carried out using known means and measures by choosing the half-value width of the primary radiators and by appropriate tuning using the reflector. Once again, primary radiators having the same design are generally used.
A disadvantage of the previously known configurations is that the phase relationship of the primary radiators is unknown and, furthermore, no defined interconnection of different primary radiators to form arrays for the purpose of influencing the radiation characteristics in a defined manner is known, inter alia as a result of this difficulty.
The preferred embodiment of the present invention provides an antenna array which comprises at least two primary radiator modules arranged vertically one above the other, and in which, with comparatively simple means, an improved implementation of a desired horizontal half-value width of the antenna array is possible.
In accordance with one aspect provided by the invention, an antenna array comprises at least two radiator modules or radiators (1, 3) arranged vertically one above the other, which are located in front of a reflector (5) and are fed by a preferably common feed network with a defined power and phase. At least one first primary radiator module or one first radiator (1) of a first type and at least one second primary radiator module or one second radiator (3) of a second type are provided, which are arranged at a distance vertically one above the other. The at least one or the plurality of primary radiator module or modules or the at least one first radiator (1) of the first type has or have a different horizontal half-value width to the at least one or the plurality of primary radiator module or modules or the at least one second radiator (3) of the second type. As a result, the overall antenna can have an overall horizontal half-value width which is different to this.
In accordance with another aspect provided by the invention, the at least one or the plurality of primary radiator module or modules or the at least one first radiator (1) of the first type has or have a different physical design to the at least one or the plurality of primary radiator module or modules or the at least one second radiator (3) of the second type.
A further aspect of this invention provides an antenna array comprising a first and a second radiator (1, 3) which are arranged vertically one above the other in front of a reflector (5) and emit in the same direction. The first radiator (1) has a different design to the second radiator (3), and the first radiator (1) also has a different horizontal half-value width to the second radiator (3). When the first radiator (1) and the second radiator (3) are being operated together, they form an overall half-value width which is different to both the half-value width of the first radiator (1) and to the half-value width of the second radiator (3) when being operated on their own.
It must be regarded as entirely surprising that the solution according to the invention makes it possible, by appropriate selection of different primary radiator modules, to tune the half-value width of such an antenna array. It should also be mentioned that, in this case, it is possible to interconnect the modules with the defined phase relationship by appropriate design of the feed network.
It is also surprising that the combination of the modules according to the invention can be used to optimize the vertical polar diagram, for example in order to achieve a reduction in the side lobes. This is possible because the at least two primary radiator modules used have different horizontal and vertical half-value widths. By interconnecting these at least two different primary radiator modules to form a linear, vertically stacked array, it is possible to adjust the horizontal half-value width of the overall antenna.
The antennas according to the invention can be constructed using primary radiator modules which comprise double dipoles and single dipoles.
The invention can be used just as well with dual-polarized antennas which, for example, operate with a +/xe2x88x9245xc2x0 polarization alignment (so-called X arrays).
If, for example, a combination of three single dipoles with a typical half-value width of 90xc2x0 and three double dipoles with a typical half-value width of 65xc2x0 corresponding to the invention is arranged vertically one above the other (thus, in other words, they are assembled to form a so-called linear, vertically stacked antenna array), then this gives a resultant horizontal half-value width of approximately 75xc2x0.
In the case of dual-polarized antennas with, for example, a +/xe2x88x92 45xc2x0 polarization alignment, a resultant horizontal half-value width of approximately 75xc2x0 can be produced and used by such a combination of cross-dipoles (horizontal half-value width of, for example, approximately 85xc2x0) and dipole squares (with a horizontal half-value width of, for example, approximately 65xc2x0).
In one preferred embodiment of the invention, the various groups of primary radiator modules in this case have considerably different horizontal half-value widths, which thus differ from one another by more than 5xc2x0, in particular by more than 10xc2x0, 15xc2x0 or 20xc2x0.
Alternatively, it is just as possible for the antenna arrays according to the invention to be formed using primary radiators in the form of patch radiators with a considerably different half-value width.
In one preferred embodiment of the invention, the primary radiators may comprise dual-polarized radiators. The primary radiators may be formed by dipole squares and cross-dipoles.
The antenna according to the invention may be used to transmit or receive in widely differing frequency bands. Normally, in the mobile radio field, such an antenna is operated in a frequency band range from 1.71 to 1.90 GHz, that is to say with a mid-frequency of about 1.80 GHz.